The present invention relates to a device for mounting a light source and more particularly to a mounting device for mounting a baseless electric lamp on a substrate in a removable fashion and a method therefore.
For a meter panel of a motorcar or a display board of various electronic control devices, a light source for display and illumination is generally used. As an example of such a light source, a baseless electric lamp (a small lamp of a crush-sealing type or a bead sealing type) is used as shown in a sectional view of FIG. 8. Namely, as shown in FIG. 8, the baseless electric lamp has a light emission filament 1, which is supported by a pair of lead wires 2a and 2b. Both ends of the lead wires 2a and 2b are sealed in a glass bulb 3. The glass bulb 3 enclosing the light emission filament 1 airtightly, crushes the other ends of the lead wires 2a and 2b at a sealing part 3a with a pincher, and airtightly derives them below from the glass bulb. More specifically, the light emission filament is composed of a coiled tungsten wire having a diameter of several tens xcexcm. The lead wires 2a and 2b supporting the light emission filament at their ends is composed of dumet wire or a nickel-coated dumet wire with a diameter of about 0.2 to 0.5 mm. The glass bulb 3 has an outer diameter of about 2.5 to 10 mm (a thickness of about 0.3 to 0.5 mm) and a length of about 3 to 10 mm.
In place of the pincher to forcibly crush the sealing part 3a, the baseless electric lamp may be formed by the following method. That is, a bead glass for supporting the lead wires 2a and 2b separately is provided at the end of the glass bulb 3 and at least either one of the bead glasses or the glass bulb 3 is fused to seal the lead wires 2a and 2b. 
Such a baseless electric lamp is mounted on a socket with a power supply terminal. The socket is then mounted on a printed circuit board for a motorcar meter board, for example, which functions as a display or illumination light source for the motorcar meter board.
FIG. 9 is a cross sectional view showing the baseless electric lamp, which is mounted on a printed circuit board. As shown in the drawing, the sealing part 3a of the baseless electric lamp is inserted into a socket 4 and the lead wires 2a and 2b are led out through a bottom 4a thereof to the other side thereof. The lead wires 2a and 2b led out through to the side of the bottom 4a are then bent respectively along an outer wall 4b of the socket 4. The socket 4 with the baseless electric lamp inserted is mounted on connection terminals (lands) 5a and 5b forming a part of the circuit of a circuit board 5 and is electrically connected as well as is mechanically fixed by solder 6. The lead wires 2a and 2b led out through the bottom 4a to the underside of the bottom 4a and bent along the outer wall 4b of the socket 4 may be guided in a grove (not shown) to form a flat surface.
As described above, the socket 4 receiving the baseless electric lamp electrically connects the electric lamp to the circuit board.
However, there is a problem in the conventional device for mounting a baseless electric lamp on a circuit board described above. Namely, there is generally a need to replace the baseless electric lamp, which is damaged or broken in the assembly course of a meter panel for a motorcar or for a display board of various electron control devices, in the course of conveying and mounting after assembled, or in the course of use after mounted. Since the baseless electric lamp is composed of thin glass bulb and the light emission filament made of a thin wire, which is easily broken with a mechanical shock, cases happen frequently where the damaged or broken baseless electric lamp must be replaced. However, in the conventional device for mounting such kind of the electric lamp, since the lead wires 2a and 2b led out through the bottom 4a of the socket 4 to the underside of it are soldered (6) to the lands 5a and 5b in the circuit board 5, the solder 6 must be fused using a soldering iron to remove the lead wires 2a and 2b from the lands 5a and 5b. 
However, such work is not only troublesome but also is apt to damage the whole circuit board. More specifically, soldering and re-soldering at the time of replacing of the baseless electric lamp give a thermal shock on the adjacent electronic parts or generate a short-circuit due to flow of the solder to the neighboring circuit board, thereby making the whole circuit board damaged.
Taking the problem described into consideration, an object of the present invention is to provide a device and a method for mounting an baseless electric lamp, in which the lamp mounted on a substrate is easily replaced.
A device for mounting a light source according to the present invention includes an electric lamp unit composed of a baseless electric lamp and a base member, and a mounting unit having a cavity for receiving the base member of the electric lamp unit.
The baseless electric lamp comprises a light emission filament, a pair of lead wires for supporting the both ends of the filament at their heads and a glass bulb in which the light emission filament and a part of the lead wires are sealed.
The base member comprises a cylindrical body having a cavity for receiving a lower part of said baseless electric lamp and supporting the pair of lead wires led out of the baseless electric lamp on its outer surface,
The mounting unit comprises a pair of conductive contact members on an inner surface of the cavity, which are connected to connection terminals on a printed circuit board at their lower ends.
The lead wires led out of the baseless electric lamp along said outer surface of said base member are made in a sliding contact with said conductive contact members when said electric lamp unit is fitted into said mounting unit.
The electric lamp unit is fitted into said mounting unit in a removable fashion.
Further, the device for mounting a light source according to the present invention includes an electric lamp unit composed of a baseless electric lamp and a base member, a mounting unit having a cavity for receiving the base member of the electric lamp unit, and a printed circuit board having a pair of connection terminals connected to a printed circuit formed on said printed circuit board.
The baseless electric lamp is composed of a light emission filament, a pair of lead wires for supporting the both ends of the filament at their heads and a glass bulb in which the light emission filament and a part of the lead wires are sealed.
The base member is composed of a cylindrical body having a cavity for receiving a lower part of said baseless electric lamp and supporting the pair of lead wires led out from the baseless electric lamp on its outer surface,
The mounting unit is composed of a pair of conductive contact members on an inner surface of the cavity, which are connected to said connection terminals on the printed circuit board at their lower ends,
The lead wires led out of the baseless electric lamp along the outer surface of the base member are made in a sliding contact with the conductive contact members when said electric lamp unit is fitted into the mounting unit.
The electric lamp unit is fitted into the mounting unit in a removable fashion.
A method for mounting a light source device on a circuit board having connection terminals for mounting said light source device on at least one main surface of the circuit board includes a step for fixing a mounting unit on said connection terminals, and a step for mounting an electric lamp unit composed of a baseless electric lamp and a base member on said mounting unit.
The mounting unit has a cavity for receiving the base member of the electric lamp unit.
The baseless electric lamp includes a light emission filament, a pair of lead wires for supporting the both ends of the filament at their heads and a glass bulb in which the light emission filament and a part of the lead wires are sealed.
The base member comprises a cylindrical body having a cavity for receiving a lower part of the baseless electric lamp and supporting the pair of lead wires led out of the baseless electric lamp on its outer surface,
The mounting unit includes a pair of conductive contact members on an inner surface of the cavity, which are connected to connection terminals on a printed circuit board at their lower ends.